1. Field of the Invention
This invention relates to improved methods of protecting ferrous metal well tubular goods and the like disposed in a well bore penetrating a subterranean producing formation.
2. Description of the Prior Art
In the treatment of subterranean producing formations, it is common to place particulate materials as a filter medium and/or a proppant in the near well bore area and in fractures extending outwardly from the well bore. In fracturing operations, particulate proppant, e.g., sand, is carried into fractures created when hydraulic pressure is applied to a subterranean rock formation to the point where fractures are developed therein. Proppant suspended in a viscosified fracturing fluid is carried outwardly away from the well bore within the fractures as they are created and extended with continued pumping. Upon release of the pumping pressure, the proppant remains in the fractures holding the separated rock faces in open positions and forming channels for the flow of produced formation fluids back to the well bore.
In unconsolidated formations, it is common to place a filtration bed of particulate gravel in the near well bore area in order to present a physical barrier to the transport of unconsolidated formation fines with the production of formation fluids. Typically, such so-called "gravel packing" operations involve the pumping and placement of a quantity of gravel and/or sand having a mesh size between about 10 mesh and 60 mesh on the U.S. Standard Sieve Series into the annulus between a screen and the walls of the well bore in an unconsolidated formation. The gravel particles form a porous matrix through which formation fluids can pass while screening out and retaining the bulk of the unconsolidated sand and/or fines transported to the near well bore area by the formation fluids.
Subterranean hydrocarbon producing formations are often stimulated by contacting the formations with an aqueous acid solution. The acid can be pumped directly into a formation to increase the hydrocarbon permeability of the formation or it can be pumped into fractures formed in a formation to produce flow channels in the fracture faces. Aqueous acid solutions are also commonly utilized as cleaning agents in the well bore to clean out perforations and to remove formation damage in the near well bore area. Heretofore, corrosion inhibitors have been added to the acid solutions used to prevent the corrosion of the ferrous metal surfaces of tubular goods and the like in the well bore. However, some acid corrosion can occur in spite of the presence of corrosion inhibitors. Also, the corrosion of the ferrous metal surfaces often takes place as a result of the production of corrosive fluids from the producing formation, e.g., aqueous acid solutions formed by the contact of produced water with acid gases such as hydrogen sulfide and carbon dioxide.
Thus, there are needs for improved methods of preventing the corrosion of ferrous metal tubular goods by acids injected into subterranean producing formations as well as acids and other corrosive fluids produced from subterranean formations.